Devices and methods for the treatment of spinal disorders

ABSTRACT

Devices and methods for treating a damaged intervertebral disc to reduce or eliminate associated back pain. The present invention provides disc reinforcement therapy (DRT) which involves implanting one or more reinforcement members in and preferably around the annulus of the disc. The reinforcement members may be used to stabilize the annulus and/or compresses a portion of the annulus so as to reduce a bulge and/or close a fissure.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. patent application Ser.No. 09/542,972, filed Apr. 4, 2000, entitled DEVICES AND METHODS FOR THETREATMENT OF SPINAL DISORDERS, and U.S. patent application Ser. No.09/685,401, filed Oct. 10, 2000, entitled DEVICES AND METHODS FOR THETREATMENT OF SPINAL DISORDERS, the entire disclosures of which arehereby incorporated by reference. The present application also claimsthe benefit of U.S. Provisional Patent Application No. 60/263,343, filedJan. 22, 2001, entitled DEVICES AND METHODS FOR THE TREATMENT OF SPINALDISORDERS.

FIELD OF THE INVENTION

The present invention generally relates to spinal implants.Specifically, the present invention relates to implantable devices andmethods for the treatment of spinal disorders associated with theintervertebral disc.

BACKGROUND OF THE INVENTION

Back pain is one of the most common and often debilitating conditionsaffecting millions of people in all walks of life. Today, it isestimated that over ten million people in the United States alone sufferfrom persistent back pain. Approximately half of those suffering frompersistent back pain are afflicted with chronic disabling pain, whichseriously compromises a person's quality of life and is the second mostcommon cause of worker absenteeism. Further, the cost of treatingchronic back pain is very high, even though the majority of sufferers donot receive treatment due to health risks, limited treatment options andinadequate therapeutic results. Thus, chronic back pain has asignificantly adverse effect on a person's quality of life, onindustrial productivity, and on heath care expenditures.

Some forms of back pain are muscular in nature and may be simply treatedby rest, posture adjustments and painkillers. For example, some forms oflower back pain (LBP) are very common and may be caused by unusualexertion or injury. Unusual exertion such has heavy lifting or strenuousexercise may result in back strain such as a pulled muscle, sprainedmuscle, sprained ligament, muscle spasm, or a combination thereof. Aninjury caused by falling down or a blow to the back may cause bruising.These forms of back pain are typically non-chronic and may beself-treated and cured in a few days or weeks.

Other types of non-chronic back pain may be treated by improvements inphysical condition, posture and/or work conditions. For example, beingpregnant, obese or otherwise significantly overweight may cause LBP. Amattress that does not provide adequate support may cause back pain inthe morning. Working in an environment lacking good ergonomic design mayalso cause back pain. In these instances, the back pain may be cured byeliminating the culprit cause. Whether it is excess body weight, a badmattress, or a bad office chair, these forms of back pain are readilytreated.

However, some forms of back pain are the result of disorders directlyrelated to the spinal column, which are not readily treated. While somepain-causing spinal disorders may be due to facet joint degradation ordegradation of individual vertebral masses, disorders associated withthe intervertebral discs are predominantly affiliated with chronic backpain (referred to as disc related pain). The exact origin of discrelated pain is often uncertain, and although some episodes of discrelated- pain may be eased with conservative treatments such as bed-restand physical therapy, future episodes of disc related pain are likely tooccur periodically.

There are a number of suspected causes of disc related pain, and in anygiven patient, one or more of these causes may be present. However, theability to accurately diagnose a specific cause or locus of pain iscurrently difficult. Because of this uncertainty, many of the causes ofdisc related pain are often lumped together and referred to asdegenerative disc disease (DDD).

A commonly suspected source of disc related pain is physical impingementof the nerve roots emanating from the spinal cord. Such nerve rootimpingement may have a number of different underlying causes, but nerveroot impingement generally results from either a disc protrusion or anarrowing of the intervertebral foramina (which surround the nerveroots).

As a person ages, their intervertebral discs become progressivelydehydrated and malnourished. Together with continued stressing, the discbegins to degenerate. With continued degeneration, or an excessivestressing event, the annulus fibrosus of the disc may tear, forming oneor more fissures (also referred to as fractures). Such fissures mayprogress to larger tears which allow the gelatinous material of thenucleus pulposus to flow out of the nucleus and into the outer aspectsof the annulus. The flow of the nucleus pulposus to the outer aspects ofthe annulus may cause a localized bulge.

When bulging of the annulus occurs in the posterior portions of thedisc, the nerve roots may be directly and physically impinged by thebulge. In more extreme or progressed instances of annular tears, thenuclear material may escape, additionally causing chemical irritation ofthe nerve roots. Depending on the cause and nature of the discprotrusion, the condition may be referred to as a disc stenosis, a discbulge, a herniated disc, a prolapsed disc, a ruptured disc, or, if theprotrusion separates from the disc, a sequestered disc.

Dehydration and progressive degeneration of the disc also leads tothinning of the disc. As the height of the disc reduces, theintervertebral foraminae become narrow. Because the nerve roots passthrough the intervertebral foraminae, such narrowing may mechanicallyentrap the nerve roots. This entrapment can cause direct mechanicalcompression, or may tether the roots, allowing them to be excessivelytensioned during body movements.

Nerve root impingement most often occurs in the lumbar region of thespinal column since the lumbar discs bear significant vertical loadsrelative to discs in other regions of the spine. In addition, discprotrusions in the lumbar region typically occur posteriorly because theannulus fibrosus is radially thinner on the posterior side than on theanterior side and because normal posture places more compression on theposterior side. Posterior protrusions are particularly problematic sincethe nerve roots are posteriorly positioned relative to theintervertebral discs. Lower back pain due to nerve root irritation notonly results in strong pain in the region of the back adjacent the disc,but may also cause sciatica, or pain radiating down one or both legs.Such pain may also be aggravated by such subtle movements as coughing,bending over, or remaining in a sitting position for an extended periodof time.

Another suspected source of disc related back pain is damage andirritation to the small nerve endings which lie in close proximity to orjust within the outer aspects of the annulus of the discs. Again, as thedisc degenerates and is subjected to stressing events, the annulusfibrosus may be damaged forming fissures. While these fissures can leadto pain via the mechanisms described above, they may also lead to painemanating from the small nerve endings in or near the annulus, due tomechanical or chemical irritation at the sites of the fissures. Thefissures may continue to irritate the small nerve endings, as theirpresence cause the disc to become structurally weaker, allowing for morelocalized straining around the fissures. This results in more relativemotion of edges of the fissures, increasing mechanical irritation.Because it is believed that these fissures have only limited healingability once formed, such irritation may only become progressivelyworse.

A common treatment for a disc protrusion is discectomy, a procedurewherein the protruding portion of the disc is surgically removed.However, discectomy procedures have an inherent risk since the portionof the disc to be removed is immediately adjacent the nerve root and anydamage to the nerve root is clearly undesirable. Furthermore, discectomyprocedures are not always successful long term because scar tissue mayform and/or additional disc material may subsequently protrude from thedisc space as the disc deteriorates further. The recurrence of a discprotrusion may necessitate a repeat discectomy procedure, along with itsinherent clinical risks and less than perfect long term success rate.Thus, a discectomy procedure, at least as a stand-alone procedure, isclearly not an optimal solution.

Discectomy is also not a viable solution for DDD when no disc protrusionis involved. As mentioned above, DDD causes the entire disc todegenerate, narrowing of the intervertebral space, and shifting of theload to the facet joints. If the facet joints carry a substantial load,the joints may degrade over time and be a different cause of back pain.Furthermore, the narrowed disc space can result in the intervertebralforamina surrounding the nerve roots to directly impinge on one or morenerve roots. Such nerve impingement is very painful and cannot becorrected by a discectomy procedure. Still furthermore, discectomy doesnot address pain caused by the fissures which may cause directmechanical irritation to the small nerve endings near or just within theouter aspect of the annulus of a damaged disc.

As a result, spinal fusion, particularly with the assistance ofinterbody fusion cages, has become a preferred secondary procedure, andin some instances, a preferred primary procedure. Spinal fusion involvespermanently fusing or fixing adjacent vertebrae. Hardware in the form ofbars, plates, screws and cages may be utilized in combination with bonegraft material to fuse adjacent vertebrae. Spinal fusion may beperformed as a stand-alone procedure or may be performed in combinationwith a discectomy procedure. By placing the adjacent vertebrae in theirnominal position and fixing them in place, relative movementtherebetween may be significantly reduced and the disc space may berestored to its normal condition. Thus, theoretically, aggravationcaused by relative movement between adjacent vertebrae may be reduced ifnot eliminated.

However, the success rate of spinal fusion procedures is certainly lessthan perfect for a number of different reasons, none of which are wellunderstood. In addition, even if spinal fusion procedures are initiallysuccessful, they may cause accelerated degeneration of adjacent discssince the adjacent discs must accommodate a greater degree of motion.The degeneration of adjacent discs simply leads to the same problem at adifferent anatomical location, which is clearly not an optimal solution.Furthermore, spinal fusion procedures are invasive to the disc, risknerve damage and, depending on the procedural approach, eithertechnically complicated (endoscopic anterior approach), invasive to thebowel (surgical anterior approach), or invasive to the musculature ofthe back (surgical posterior approach).

Another procedure that has been less than clinically successful is totaldisc replacement with a prosthetic disc. This procedure is also veryinvasive to the disc and, depending on the procedural approach, eitherinvasive to the bowel (surgical anterior approach) or invasive to themusculature of the back (surgical posterior approach). In addition, theprocedure may actually complicate matters by creating instability in thespine, and the long term mechanical reliability of prosthetic discs hasyet to be demonstrated.

Many other medical procedures have been proposed to solve the problemsassociated with disc protrusions. However, many of the proposedprocedures have not been clinically proven and some of the allegedlybeneficial procedures have controversial clinical data. From theforegoing, it should be apparent that there is a substantial need forimprovements in the treatment of spinal disorders, particularly in thetreatment of disc related pain associated with a damaged or otherwiseunhealthy disc.

SUMMARY OF THE INVENTION

The present invention addresses this need by providing improved devicesand methods for the treatment of spinal disorders. The improved devicesand methods of the present invention specifically address disc relatedpain, particularly in the lumbar region, but may have other significantapplications not specifically mentioned herein. For purposes ofillustration only, and without limitation, the present invention isdiscussed in detail with reference to the treatment of damaged discs inthe lumbar region of the adult human spinal column.

As will become apparent from the following detailed description, theimproved devices and methods of the present invention may reduce if noteliminate back pain while maintaining near normal anatomical motion.Specifically, the present invention provides disc reinforcement devicesto reinforce a damaged disc, while permitting relative movement of thevertebrae adjacent the damaged disc. The devices of the presentinvention are particularly well suited for minimally invasive methods ofimplantation.

The reinforcement devices of the present invention may provide threedistinct functions. Firstly, the reinforcement devices may mechanicallystabilize and strengthen the disc to minimize if not eliminate chronicirritation of nerve roots and nerves around the periphery of the discannulus. Secondly, the reinforcement devices may radially and/orcircumferentially compress the disc to close fissures, fractures andtears, thereby preventing the ingress of nerves as well as potentiallyfacilitating healing. Thirdly, the reinforcement devices may be used tostabilize the posterior disc after a discectomy procedure in order toreduce the need for re-operation.

In an exemplary embodiment, the present invention provides discreinforcement therapy (DRT) in which a reinforcement member is implantedin the annulus of an intervertebral disc. The implantation method may beperformed by a percutaneous procedure or by a minimally invasivesurgical procedure. The present invention provides a number or tools tofacilitate percutaneous implantation. One or more reinforcement membersmay be implanted, for example, posteriorly, anteriorly, and/orlaterally, and may be oriented circumferentially or radially. As such,the reinforcement members may be used to stabilize the annulus and/orcompresses a portion of the annulus so as to reduce a bulge and/or closea fissure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate left lateral and posterior views,respectively, of a portion of the adult human vertebral (spinal) column;

FIGS. 2A and 2B illustrate superior (top) views of a healthy disc and adegenerated disc, respectively, and an adjacent vertebral body;

FIGS. 3A-3F schematically illustrate superior (top) views ofreinforcement members disposed in degenerated discs;

FIG. 4A-4M schematically illustrate various features that may beincorporated into a straight or curved reinforcement member inaccordance with an embodiment of the present invention;

FIGS. 5A-5C schematically illustrate a circumferential reinforcementmember in accordance with an embodiment of the present invention;

FIGS. 6A-6H schematically illustrate components of a reinforcementmember in accordance with an embodiment of the present invention;

FIGS. 7A-7F illustrate tools of the present invention for implanting thereinforcement members shown in FIGS. 3A and 33B in accordance with themethod illustrated in FIGS. 8A-8L;

FIGS. 8A-8L illustrate a method for implanting the reinforcement membersshown in FIGS. 3A and 3B in accordance with an embodiment of the presentinvention;

FIGS. 9A-9F illustrate tools of the present invention for implanting thereinforcement member shown in FIG. 3C in accordance with the methodillustrated in FIGS. 10A-10H;

FIGS. 10A-10H illustrate a method for implanting the reinforcementmember shown in FIG. 3C in accordance with an embodiment of the presentinvention;

FIGS. 11A-11H illustrate a method for implanting the reinforcementmember shown in FIG. 3D in accordance with an embodiment of the presentinvention;

FIGS. 12A-12G and 13-15 illustrate various tools of the presentinvention for implanting the reinforcement member shown in FIGS. 3E and3F in accordance with the method illustrated in FIGS. 18A-18L;

FIGS. 16A-16E illustrate a column support and advancement device for usewith the tools illustrated in FIGS. 12A-12G and 13;

FIGS. 17A-17D illustrate an alternative column support and advancementdevice for use with the tools illustrated in FIGS. 12A-12G and 13;

FIGS. 18A-18L illustrate a method for implanting the reinforcementmember shown in FIGS. 3E and 3F in accordance with an embodiment of thepresent invention;

FIGS. 19A-19F illustrate various possible implant orientations of thereinforcement member shown in FIGS. 3E and 3F;

FIGS. 20A-20J illustrate steps for implanting a self-expandingreinforcement member;

FIGS. 20K-20L illustrate steps for implanting an inflatablereinforcement member;

FIGS. 20M-20R illustrate steps for implanting a reinforcement bar;

FIGS. 21A-21C illustrate a reinforcement member in accordance with analternative embodiment of the present invention; and

FIGS. 22A-22D illustrate a reinforcement member in accordance with yetanother alternative embodiment of the present invention;

DETAILED DESCRIPTION

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

With reference to FIGS. 1A and 1B, the lower portion of an adult humanvertebral column 10 is illustrated in left lateral and posterior views,respectively. The upper portion of the vertebral column 10 includes thethoracic region and the cervical region, which are not shown forpurposes of simplified illustration only. The lower portion of thevertebral column 10 includes the lumbar region 12, the sacrum 14 and thecoccyx 16. The sacrum 14 and the coccyx 16 are sometimes collectivelyreferred to as the pelvic curvature.

The vertebral column 10 includes an axis of curvature 60 which generallyforms a double-S shape when viewed laterally. The vertebral column 10also includes a median plane 70 which is a sagittal plane bisecting thevertebral column 10 into symmetrical left lateral and right lateralportions. In posterior views, the median plane 70 appears as a line.

The lumbar region 12 of the vertebral column 10 includes five (5)vertebrae 20 (labeled L1, L2, L3, L4 and L5) separated by intervertebraldiscs 50. The sacrum 14, which includes five (5) fused vertebrae 30(superior vertebra 30 labeled S1), is separated by a single disc 50 fromthe coccyx 16, which includes four (4) fused vertebrae 40.

Although not labeled, the intervertebral discs 50 may be referenced bytheir respective adjacent vertebrae. For example, the disc 50 betweenthe L4 and L5 lumbar vertebrae 20 may be referred to as the L4L5 disc.Similarly, the disc 50 between the L5 lumbar vertebra 20 and the S1sacral vertebra 30 may be referred to as the L5S1 disc.

Although each vertebra 20/30/40 is a unique and irregular bonestructure, the vertebrae 20 of the lumbar region 12 (in addition to thethoracic and cervical regions) have common structures. Each vertebra 20of the lumbar region 12 generally includes a body portion 21 and avertebral arch portion 22/23 which encloses the vertebral foramen (notvisible) in which the spinal cord is disposed. The vertebral arch 22/23includes two pedicles 22 and two laminae 23. A spinous process 24extends posteriorly from the juncture of the two laminae 23, and twotransverse processes 25 extend laterally from each lamina 23. Fourarticular processes 26/27 extend inferiorly 26 and superiorly 27 fromthe laminae 23. The inferior articular process 26 rests in the superiorarticular process 27 of the adjacent vertebra to form a facet joint 28.

The five (5) vertebrae 30 of the sacrum 14 are fused together to form asingle rigid structure. The sacrum 14 includes a median sacral crest 31which roughly corresponds to the spinous processes of the vertebrae 30,and two intermediate sacral crests 32 which roughly correspond to thearticular processes of the vertebrae 30. The sacral laminae 33 aredisposed between the median 31 and intermediate 32 sacral crests. Twolateral sacral crests 34 are disposed on either side of the sacralforaminae 35. The sacrum 14 also includes a pair of sacral wings 36which define auricular surfaces 39. The superior (S1) sacral vertebra 30includes two superior articular processes 37 which engage the inferiorarticular processes 26 of the L5 lumber vertebra 20 to form a facetjoint, and the base 38 of the superior sacral vertebra S1 is joined tothe L5S1 disc 50.

With reference to FIG. 2A, each intervertebral disc 50 includes anannulus fibrosus 52 surrounding a nucleus pulposus 54. The posteriorannulus 52 is generally thinner than the anterior annulus 52, which mayaccount for the higher incidence of posterior disc protrusions. Theannulus fibrosus 52 comprises about 60% of the total disc 50cross-sectional area, and the nucleus pulposus 54 only comprises about40% of the total disc 50 cross-sectional area. The annulus fibrosus 52comprises 40-60% organized collagen in the form of a laminatedstructure. The nucleus pulposus 54 comprises 18-30% collagen in the formof a relatively homogenous gel.

A common theory is that each intervertebral disc 50 forms one supportpoint and the facet joints 28 form two support points of what may becharacterized as a three point support structure between adjacentvertebrae 20. However, in the lumbar region 12, the facet joints 28 aresubstantially vertical, leaving the disc 50 to carry the vast majorityof the load. As between the annulus fibrosus 52 and the nucleus pulposus54 of the disc 50, it is commonly believed that the nucleus 54 bears themajority of the load. This belief is based on the theory that the disc50 behaves much like a balloon or tire, wherein the annulus 22 merelyserves to contain the pressurized nucleus 54, and the nucleus 54 bearsall the load. However, this theory is questionable since the annulusfibrosus 52 comprises 60% of the total disc 50 cross-sectional area andis made of 40-60% organized collagen in the form of a laminatedstructure. By contrast, the nucleus pulposus 54 only comprises 40% ofthe total disc 50 cross-section and is made of 18-30% collagen in theform of a relatively homogenous gel. Thus, a more plausible theory isthat the annulus fibrosus 52 is the primary load bearing portion of thedisc 50.

With reference to FIG. 2B, the intervertebral discs 50 becomeprogressively dehydrated and malnourished with age. When combined withcontinued stressing, the disc begins to degenerate. With continueddegeneration, or an excessive stressing event, the annulus fibrosus ofthe disc may tear, forming one or more radial fissures 56 orcircumferential fissures 58, which may progress to larger tears. Largertears may allow the gelatinous material of the nucleus pulposus 54 toflow out of the nucleus and into the outer aspects of the annulus 52.The flow of the nucleus pulposus 54 to the outer aspects of the annulus52 may cause a localized bulge 60. A posterior bulge 60 may result indirect impingement of a nerve root (not shown). Nuclear material thatescapes through an advanced tear may cause further mechanical irritationand additionally cause chemical irritation of a nerve root. A nerve rootmay also be compressed or tethered by a narrowing of the intervertebralforaminae, resulting from a loss in disc height caused by sustaineddegeneration of the disc 50. Small nerve endings (not shown) in or nearthe perimeter of the annulus 52 may also be mechanically or chemicallyirritated at the sites of the fissures 56/58. In all cases, degenerationof the disc eventually leads to disc related pain of some origin.

FIGS. 3A-3F schematically illustrate reinforcement members100/200/300/600 implanted in a degenerated disc 50. In all instances,the reinforcement members 100/200/300/600 mechanically stabilize andstrengthen the disc 50 to minimize if not eliminate chronic irritationof nerve roots and nerves around the periphery of the disc annulus 52.As can be seen in FIGS. 3A-3F, the reinforcement members 100/200/300/600also radially and/or circumferentially compress the disc 50 to closefissures 56/58, thereby preventing the ingress of nerves and potentiallyfacilitating healing. The reinforcement members 100/200/300/600 mayfurther be used to stabilize the posterior portion of the disc 50 aftera discectomy procedure in order to reduce the need for re-operation.

FIGS. 3A-3F show examples of where the reinforcement members100/200/300/600 may be implanted in the annulus 52. However, thereinforcement members 100/200/300/600 may be implanted in any portion ofthe annulus 52 including, without limitation, the posterior, anterior orlateral portions thereof. Because most disc related pain is associatedwith damage to the posterior portion of the disc 50, the reinforcementmembers 100/200/300/600 preferably provide support to the posteriorportion of the annulus 52 and establish anchor points in the lateral andanterior portions of the annulus 52, or completely encircle the annulus52. The reinforcement members 100/200/300/600 may be used individuallyas shown in FIGS. 3A and 3C-3F, or in combination as shown in FIG. 3B.Although not shown, any combination of the different types ofreinforcement members 100/200/300/600 may be utilized.

The reinforcement members 100/200/300/600 may be oriented generallyparallel to the periphery of the annulus 52 (e.g., reinforcement members100A, 100C, 200, 300, 600), generally radial to the annulus 52 (e.g.,reinforcement member 100B), or any other orientation suitable forstabilizing and/or compressing the desired portion(s) of the annulus 52.Generally, the closer the reinforcement members 100/200/300/600 are tothe periphery of the annulus 52, the greater the amount of support andstabilization provided to the disc 50. As such, the reinforcementmembers 100/200/300/600 preferably have a curvature conforming to theperiphery of the annulus 52 such that they may be implanted as close tothe periphery of the annulus 52 as possible. The reinforcement members100/200/300/600 may have such a curvature in the relaxed (zero stress)state, or the curvature may be imparted by the insertion path or definedby the insertion tools used.

The reinforcement members 100/200/300/600 may extend across and closefissures 56/58 as shown, or any other portion of the annulus 52 toprovide compression and stabilization of the disc 50. Although notshown, the reinforcement members 100/200/300/600 may extend across orinto the nucleus 54. In such a case, it is preferred that thereinforcement members 100/200/300/600 do not extend outside theperiphery of the annulus 52 in order to reduce the probability ofnuclear material escaping from the outer aspects of the annulus 52.

The reinforcement members 100/200/300/600 are sized to fit within theannulus 52 of a human disc 50. Thus, the collective diameter and lengthof the reinforcement members 100/200/300/600 implanted preferably doesnot exceed the height and circumference/diameter, respectively, of theannulus 52, depending on the number and orientation of the reinforcementmembers 100/200/300/600 implanted. The reinforcement members100/200/300/600 may be made of a biocompatible material or coated with abiocompatible material. Suitable structural materials for thereinforcement members 100/200/300/600 include stainless steel and superelastic alloys such as nickel titanium. All or a portion of thereinforcement members 100/200/300/600 may be made of biodegradable orbioabsorbable material such as resorbable collagen, LPLA(poly(1-lactide)), DLPLA (poly(dl-lactide)), LPLA-DLPLA, PGA(polyglycolide), PGA-LPLA or PGA-DLPLA. Other metals, alloys, polymers,and composites having suitable tensile, compression and fatigue strengthand elasticity may also be used. The reinforcement members100/200/300/600 may further include growth factors to facilitatehealing, agents which render nuclear matter inert or otherwise reducechemical irritation thereof, and/or anesthetic agents to reduce nervesignal transmission (i.e., pain).

Reinforcement member 600, as illustrated in FIGS. 3E and 3F, is adaptedto completely encircle the annulus 52 to thereby apply uniformcompressive forces about the periphery of the annulus 52. Thereinforcement member 600 has opposing ends which are secured together bya permanent connection 610 such as a knot as seen in FIG. 3E.Optionally, a pledget 750 may be employed as illustrated in FIG. 3F andas discussed in more detail hereinafter. Reinforcement member 600 maysubstantially reside within the confines of the annulus 52, with theconnection 610 and optional pledget 750 residing within or immediatelyoutside the confines of the annulus 52. While reinforcement member 600is shown within the outer aspect of the annulus 52, it is alsocontemplated that all or portions of reinforcement member 600 may beimplanted outside the annulus 52. For example, reinforcement member 600may be placed in the tissue plane between the outside of the annulus 52and external connective tissues (not shown).

The reinforcement member 600 may comprise a monofilament ormultifilament structure that resists elongation in tension, but isotherwise very flexible. For example, the reinforcement member 600 maycomprise a polymeric or metallic fiber, cable, thread, suture, wire,ribbon, or the like. Suitable materials for the circumferentialreinforcement member 600 include, but are not limited to, commerciallyavailable suture materials used in a variety of surgical procedures.Such exemplary suture materials include biodegradable suture made frompolylactic acid and polyglycolic acid, and nondegradable materials suchas monofilament and braided polypropylene and polyester (PET). Anothersuitable non-degradable suture material is made from expandedpolytetrafluoroethylene (ePTFE). Other materials which are suitable forthe circumferential reinforcement member 600 include braided ultra-highmolecular weight fibers of polyethylene (UHMWPE), commercially availableas Spectra™ or Dyneema™, as well as other high tensile strengthmaterials such as Vectran™, Kevlar™, and natural or artificiallyproduced silk.

As an alternative, the reinforcement member 100/200/300/600 may bedesigned for temporary heating (post-implantation) to cause thermalchanges to the annulus. Because the annulus is comprised of overlappingbands of oriented collagen which tend to shrink in the direction oforientation when heated to temperatures of 50 to 90 degrees centigrade,temporarily heating the reinforcement member 100/200/300/600 causesthermal reformation of the annulus. In addition, annular defects such asfissures and tears can refuse, particularly if the edges are broughtinto apposition prior to or during the heating step. Such annulardefects may be closed (i.e., edges brought into apposition) bycompression imparted by the reinforcement member 100/200/300/600 duringimplantation or by collagen shrinkage imparted by heating thereinforcement member 100/200/300/600.

The reinforcement member 100/200/300/600 may be heated by inducing heatin the material of the reinforcement member 100/200/300/600 or byincorporating one or more heating elements into the reinforcement member100/200/300/600. In both cases, a source of electric or magnetic power(e.g., electric power supply, magnetic field generator, RF transmitter,etc.) is used to provide energy to the reinforcement member100/200/300/600 which converts the electric/magnetic energy to thermalenergy. Such a power source may be directly or remotely connected to thereinforcement member 100/200/300/600.

For example, the reinforcement members 100/200/300/600 may includeresistive heating elements directly connected to an internal (implanted)power supply or directly connected (transdermal) to an external electricpower supply. Alternatively, the resistive heating elements may beconnected to an implanted receiving antenna which receives a powersignal from a remote external power signal transmitting antenna. As afurther alternative, the reinforcement member 100/200/300/600 may beheated by remote inductive heating via an external alternating magneticfield generator. Because significant portions of the reinforcementmember 100/200/300/600 may comprise a conductive metallic material, thepresence of an alternating magnetic field will inductively heat thereinforcement member 100/200/300/600. Further aspects of these and otherheated reinforcement member 100/200/300/600 embodiments are discussed inmore detail with reference to FIGS. 4H-4M.

In all embodiments, various visualization techniques may be used tofacilitate implantation of the reinforcement members 100/200/300/600.For example, real time CT scanning, real time MR imaging, or acombination of preoperative CT or MR images superimposed onto a realtime device tracking images such as the system commercially availableunder the trade name STEALTH™ available from Sofamor Danek.

FIGS. 4A-4K illustrate various embodiments of the reinforcement member100 in accordance with the present invention. The embodiments of FIGS.4A-4K illustrate various features which may be combined in any way toprovide the desired reinforcement member 100. Reinforcement member 100may be sized and oriented as shown and discussed with reference to FIGS.3A and 3B. Reinforcement member 100 includes a body portion 110 and ananchor 120. The anchor 120 serves to immobilize or limit movement of thereinforcement member 100 relative to the annulus 52.

In FIGS. 4A, 4D and 4F, the anchor is in the form of threads 122disposed about the periphery of the body portion 110, which behave likethreads on a screw and engage the annulus 52 upon rotation therein. Whenthreads 122 are used, the proximal end of the body 110 may include slots116 as shown in FIG. 4C, which is an end view taken along line 4C—4C inFIG. 4A. The slots 116, or any other suitable mating geometry,facilitate rotation with a driver having a mating distal end. In FIG.4E, the anchor 120 is in the form of sloped rings 124 spaced along thelength of the body portion 110, which behave like rings on a ring-shanknail to engage the annulus 52 upon pushing therein. Those skilled in theart will recognize that other anchor 120 mechanisms such as barbs,expandable anchors, etc. may also be used.

The anchor 120 may extend the full length of the body portion 110 asshown in FIGS. 4A and 4F, or may be disposed only on proximal and distalportions of the body as shown in FIGS. 4D and 4E. The body portion 1 10may be tubular defining a lumen 112 extending therethrough as shown inFIG. 4B, which is a cross-sectional view taken along line 4B—4B in FIG.4A. The lumen 112 facilitates advancement of the reinforcement member100 over a stylet to facilitate insertion into the annulus 52, as willbe discussed in greater detail hereinafter. Alternatively, the bodyportion 110 may have a solid cross-section as shown in FIG. 4G, which isa cross-sectional view taken along line 4G—4G in FIG. 4F. In thisalternative embodiment, the solid cross-section body portion 110 mayinclude a sharpened distal tip 114 as shown in FIG. 4F to facilitateinsertion into the annulus 52.

Preferably, the threads 122 have a variable pitch such that the annulusis compressed as the reinforcement member 100 is rotated and advancedinto the annulus 52. Variable pitch threads 122, as shown in FIGS. 4A,4D and 4F, generally have a larger pitch at the distal end of the body110 and a smaller pitch at the proximal end of the body 110. The largerpitch distal threads 122 pull the annular tissue 52 a greater distanceper revolution than the smaller pitch proximal threads 122. Thus, as thereinforcement member 100 is rotated and advanced into the annulus 52,the distal threads pull the annular tissue together and the proximalthreads hold the tissue in place thereby compressing the annulus 52. Bycompressing the annulus 52, the disc 50 is mechanically stabilized andthe fissures 56/58 are closed to facilitated healing.

Although compression of the annulus 52 is preferred, it is not necessaryto have compression in order to provide some degree of mechanicalstabilization. To the extent that compression is desired, the variablepitch threads 122 mentioned above are currently preferred. However,other compression techniques are equally useful. For example, standardconstant pitch threads 122 and tapered rings 124 may achieve compressionby utilizing a step-wise advancement and tension technique as will bedescribed in more detail hereinafter.

In order to provide the ability to temporarily heat the reinforcementmember 100 as discussed previously, various modifications to the designof the reinforcement member 100 may be made as described with referenceto FIGS. 4H-4M. These design modifications may also be applied toreinforcement members 200 and 300, but are described with specificreference to reinforcement member 100 for purposes of illustration only.Although numerous methods may be employed to temporarily heat thereinforcement member 100, two preferred methods, resistive heating andinductive heating are described in detail.

FIG. 4H illustrates a generic reinforcement member 100 including bodyportion 110, anchors 120 (not shown for sake of clarity) and heatingelement 140 in the form of a resistive wire. FIG. 41 is across-sectional view taken along line 41—41 in FIG. 4H. Resistive wire140 may be helically wound on the outer surface of the body 110, theinner surface of the body 110, or in the wall of the body 110.Preferably resistance wire 140 is helically incorporated into the wallof the body portion 110 at the time of fabrication, for example byinsert/injection molding. Resistance wire 140 may helically traverse thelength of the body 110 in one pitch direction, then traverses back inthe opposite direction in an opposite pitch direction. In this manner, asingle wire traverses the length of the body 110, but has two ends atthe proximal end of the body 110 available for connection to anelectrical power source or receiving antenna.

Resistance wire 140 is conductive, but offers a high enough resistanceto heat during the application of electrical current. The wire may bemade of a variety of conductive metals, including copper, tungsten,platinum, or gold, and may be covered/coated with a biocompatiblematerial. Preferably, the resistance wire 140 is formed of abiocompatible metal, but this is not essential as long as direct tissueexposure is avoided such as when a biocompatible covering/coating isused or when the wire 140 is embedded in the wall of body 110. Since thewire will be heated to a relatively high temperature (e.g., 50 to 90degrees centigrade), the body 110 or covering is preferably made of amaterial which can withstand elevated temperatures, preferably of a hightemperature polymer such as Polyimide, PTFE, Kynar, or PEEK.

Electrification of resistance wire 140 may be accomplished by initiallyincorporating a pair of releasable low resistance lead wires 142 to theends of the resistance wire 140, as shown in FIG. 4H. The lead wires 142are passed through or reside alongside driver 440 during the advancementof reinforcement member 100 as described with reference FIGS. 8A-8L. Ifthey are passed through the driver 440, the driver must be hollow. Oncethe reinforcement member 100 is fully implanted, the lead wires 142 areconnected to a power source 146, which delivers electrical current tothe reinforcement member 100, causing it and the surrounding tissue toheat to a desired temperature for a desired period of time. Thetemperature of the resistance wire 140 may be monitored by measuring thecurrent demand from the power source 146 or by positioning athermocouple (not shown) adjacent the proximal end of the reinforcementmember 100. Once the heating step is finished, the releasable leads 142are removed from the resistance wires 140 utilizing releasableconnection 141. Removal of the releasable leads 142 may be accommodatedby providing a low tensile strength connection which separates bypulling, or by providing a fusible metal strip connection whichseparates by applying electric current above a threshold value. Such afusible metal strip connection may also serve to self-limit the degreeto which the reinforcement member is heated.

Alternatively, the leads 142 are not removable, but stay attached to theresistive wires 140 and reinforcement member 100, as illustrated in FIG.4J. In this embodiment, and preferably after the reinforcement member100 is implanted, the leads 142 are attached to an implantable receiverantenna such as conductive wire coil 144. The receiver coil 144 may beincorporated into a housing 145 having a flat disc shape which issubcutaneously positioned adjacent the access site. Since the lead wires142 and the receiver coil 144 are implanted within the body, the housing145 and the lead wires 142 are preferably encased in a biocompatible andstable material, for example silicone rubber.

FIG. 4K illustrates an example of a suitable implant position for thereceiver coil 144, relative to the vertebral column 10, preferablyadjacent the lumbar disc being treated. The receiver coil 144 andhousing 145 are oriented parallel to the surface of the skin, and theaccess site is then closed. Once positioned, a similarly shapedtransmitting coil 148 is placed on the skin surface, adjacent andoverlapping the subcutaneous receiver coil 144. The transmitting coil148 is connected to a power source 146 and associated transmissioncircuit. When an alternating current is delivered to the transmittingcoil 148, a corresponding alternating current is generated in thereceiving coil 144, which in turn causes the resistance wire 140 and thereinforcement member 100 to heat.

One advantage of this resistive heating method is that the heatingprocedure can be repeated multiple times, without the need forreoperation or any other invasive procedure. For example, the patientmay have the implanted reinforcement member(s) 100 heated upon initialimplantation, and have them re-heated at any such time as back pain mayrecur. One of the mechanisms by which heat is believed to minimize backpain is by the destruction of nerve endings at the periphery of theannulus. However, new nerve endings may permeate the annulus,necessitating a subsequent heating to return the patient to a pain-freestate.

As an alternative to the antennas 144/148, a transdermal plug 149 may beused to establish direct connection between the leads 142 and the powersource 146. The plug 129 includes an internal implantable portion and anexternal portion. To facilitate immediate heating of the reinforcementmember 100, the internal and external portions of the plug 129 may beconnected just after implantation of the reinforcement member 100, butprior to closing the access site. The internal portion of the plug 129is then positioned just below the skin and the access site is closed. Tofacilitate post-operative heating, a small incision may be made in theskin to connect the internal and external portions of the plug 129.

An alternate method of heating reinforcement member 100 and surroundingannular tissue is the use of inductive heating. Inductive heating isused in many industrial and some medical applications. Essentially, ahigh frequency alternating magnetic field is oriented on the object tobe heated. The alternating magnetic field causes eddy currents in theobject to be heated. These eddy currents then cause ohmic heating. Aslong as the object to be heated is conductive, usually metallic, it maybe inductively heated.

To facilitate inductive heating, all or a significant portion ofreinforcement member 100 is fabricated of a conductive metal, such asstainless steel, carbon steel, MP35N, nickel titanium alloy, ortungsten. The choice of material will influence the parameters neededfor the inducting power source. Preferably, the entire body 110 isfabricated of the conductive metal.

With reference to FIG. 4M, the inductor may include a power source 152coupled by leads 154 to a coil 150 which generates a large alternatingmagnetic field. The coil 150 may have a long tubular shape, inside whichthe patient resides during heating, or may be of a smaller size (asillustrated) which is oriented toward the reinforcement member 100. Themain parameters which need to be adjusted to result in a desired heatingof the reinforcement member 100 are the frequency and amplitude of thealternating magnetic field. Typical frequencies will range from about 10kHz to 10 MHz. Inductive heating also has the advantage of allowing formultiple subsequent heating treatments for the patient, should back painrecur.

While the reinforcement member 100 is preferably a permanently implanteddevice, the incorporation of temporary heating immediately or shortlyafter implantation allows for the possibility of temporary implantation.In this usage of reinforcement member 100, it is implanted using themethods and tools described in further detail below. But, once fullyimplanted, a transient heating step is performed. Because thereinforcement member causes the annular tissue to compresscircumferentially and/or radially, the heating is particularly effectiveat remodeling the annular tissue to a more normal, pre-degeneratedcondition. Therefore, it may not be necessary to keep the reinforcementmember implanted. The reinforcement member 100 can be removed byessentially reversing the implantation steps. In order to facilitateremoval following heating, it is desirable to provide a lubriciouscoating such as a hydropholic polymer or PTFE coating on the surface ofthe reinforcement member 100, including the body 110 and anchor 120.

FIGS. 5A-5C schematically illustrate a circumferential reinforcementmember 200, which is generally the same as reinforcement member 100except as described herein. FIG. 5B is a cross-sectional view takenalong line 5B—5B in FIG. 5A, and FIG. 5C is an end view taken along line5C—5C in FIG. 5A. The circumferential reinforcement member 200 includesa tubular body 210 defining a lumen 212 to facilitate advancement over astylet. The circumferential reinforcement member 200 also includes ananchor 220, preferably in the form of variable pitch threads 222. Theproximal end of the body 210 the may include slots 216 or other suitablemating geometry to facilitate rotation by a driver having a matingdistal end. Any of the variants of reinforcement member 100 discussedwith reference to FIGS. 4A-4G may be applied to circumferentialreinforcement member 200.

The circumferential reinforcement member 200 may have a geometry (e.g.,circle, ellipse, oval, etc.) corresponding to the geometry of the outeraspects of a healthy annulus 52, or the member 200 may be naturallystraight, taking on a curved shape during implantation. Because thecircumferential reinforcement member 200 is implanted in the annulus 52around the entire periphery thereof, the reinforcement member maximizesanchoring strength and provides superior stabilization around the entiredisc 50. Thus, it is preferable that the reinforcement member 200 definea closed geometry once implanted, or even have overlapping ends, but anopen geometry (e.g., semi-ellipse or semi-circle) may also be employed.The size and shape of the reinforcement member 200 may be pre-selectedto accommodate anatomical variations of the annulus 52 between patients.The reinforcement member may have a relaxed size that is smaller thanthe implanted size such that additional radial and circumferentialcompression is achieved.

Circumferential reinforcement member 200 may further incorporate designfeatures which allow for temporary heating. As described in connectionwith reinforcement 100 above, similar features which allow for resistiveheating or inductive heating may be incorporated.

FIGS. 6A-6H schematically illustrate reinforcement member 300, includinga pair of tubular pins 310, two screws 320 and two connecting rings 330which may be assembled as shown in FIG. 6F. With reference to FIG. 6A,each of the tubular pins 310 includes a shaft portion 312, a headportion 314 and a connection mechanism 318. The shaft 312 is sized tofit within a hole of the connection ring 330 and the head 314 is sizedlarger than the same hole. The connection mechanism 318 may comprises athreaded shaft insertable into a threaded hole as shown, or any otherknown mechanical releasable connection that maintains the profile of theshaft portion 312. As seen in FIG. 6B, which is a cross-sectional viewtaken along line 6B—6B in FIG. 6A, the shaft portion 312 includes alumen 313 to facilitate advancement over a stylet. The heads 314 mayeach include a slot 316 as seen in FIG. 6C, which is an end view takenalong line 6C—6C in FIG. 6A, or other suitable geometry to mate with adistal end of a driver to facilitate rotation of the pins 310 to screwthe releasable connection together.

The screws 320 include a shaft 322, a head 324, threads 328 and asharpened tip 323 as seen in FIG. 6D. The screws 320 may comprise a widevariety of orthopedic screw designs, particularly those suitable forimplantation into cartilage and other collagen-based tissues. The shaft322 and threads 326 are sized to fit within a hole of the connectionring 330 and the head 324 is sized larger than the same hole. The head324 includes slots 326 as seen in FIG. 6E, which is an end view takenalong line 6E-6E in FIG. 6D, or other suitable mating geometry tofacilitate rotation by a driver having a mating distal end.

The connection rings 330 each have first and second rings 331/333defining first and second holes 332/334 as shown in FIG. 6F. The firsthole 332 is sized to provide a sliding fit about the shaft 312 of thepins 310 and the second hole is sized to provide a sliding fit about theshaft 322 and threads 326 of the screws 320. As seen in the side viewshown in FIG. 6G, each of the connection rings 330 also define an angle336 between the rings 331/333 to accommodate the implanted arrangementas shown in FIG. 6H.

As described above in connection with reinforcement members 100 and 200,reinforcement member 300 can also incorporated features to provide fortemporary heating. For example, tubular pins 310 can incorporateresistive wire, or can be fabricated of a conductive metallic material,in a manner similar to that described for reinforcement members 100 or200 above.

Referring now to FIGS. 7A-7F, various tools 410, 420, 430 and 440 areshown individually and assembled. The tools 410, 420, 430 and 440 may beused to implant the reinforcement members 100 discussed above. The toolsinclude a rigid, sharpened, hollow trocar 410 as shown in FIG. 7A, asemi-rigid, sharpened, hollow curved needle 420 as shown in FIG. 7B, asharpened curved stylet 430 as shown in FIG. 7C, and a hollow driver 440as shown in FIG. 7D. As seen in FIG. 7E, the sharpened stylet 430 fitsinto the semi-rigid needle 420 which fits into the rigid trocar 410. Asseen in FIG. 7F, the sharpened stylet 430 fits into the hollow driver440 which fits into the rigid trocar 410.

With specific reference to FIG. 7A, the rigid hollow trocar 410 includesa hollow shaft 412 and a grip or handle 414. The shaft 412 includes asharpened tip 413 to facilitate passage through the skin and backmuscles, and insertion into the annulus 52. The shaft 412 is preferablymade of a rigid metal such as a stainless steel hypodermic tube. Thegrip 414 may comprise a polymer and may be formed by insert injectionmolding with the shaft 412 inserted into the mold.

With specific reference to FIG. 7B, the semi-rigid curved needle 420includes a hollow shaft 422 a hub 424. The shaft 422, which includes asharpened tip 423, is longer than the rigid trocar 410 and has anoutside diameter sufficiently small to fit into the rigid trocar 410.The shaft 422 is preferably made of a semi-rigid polymer or composite.The shaft 422 includes a curved distal portion 426 that may bestraightened (shown in phantom) upon insertion of the semi-rigid needle420 into the lumen of the rigid trocar 410. The hub 424 may include afitting 425 to facilitate connection to a fluid source or a pressuresource (e.g., a syringe).

With specific reference to FIG. 7C, the sharpened curved stylet 430includes a flexible shaft 432 and a sharpened distal end 433. The distaltip 433 may optionally include an anchor 435 such as threads, taperedrings or barbs to facilitate the step-wise advancement and tensiontechnique as will be described in detail hereinafter. If threads areused for the anchor 435, the curvature 434 of the distal portion of theshaft 432 may be eliminated to facilitate efficient torque transfer. Theshaft 432 includes a curve 434 which approximates the curvature anddiameter of the outer aspects of the annulus where the reinforcementmember 100 is to be implanted. The shaft 432 is longer than the both therigid trocar 410 and the semi-rigid needle 420, and may have a length onthe order of 10 to 60 cm. The shaft 432 also has an outside diametersufficiently small to fit into the semi-rigid needle 420. The shaft 422preferably has a flexible but pushable construction incorporating arigid metal such as stainless steel, or super-elastic nickel-titaniumalloy. The sharpened stylet 430 is preferably highly elastic, to resistpermanent set upon insertion into the curved portion 426 of thesemi-rigid needle 420.

With specific reference to FIG. 7D, the hollow driver 440 includes ahollow shaft 442 and a grip or handle 444. The distal end of the hollowshaft 442 includes a tip 446 defining a geometry which mates with an endof the reinforcement member 100 to facilitate rotation thereof duringimplantation. The shaft 442 is preferably made of a torsionally rigidmetal such as a stainless tool steel. The grip 444 may comprise apolymer and may be formed by insert injection molding with the shaft 442inserted into the mold.

With general reference to FIGS. 8A-8L, the steps for implantingreinforcement member 100 are illustrated. It should be understood thatthe procedure for implanting a single member 100 in the posteriorportion of the annulus 52 is shown for purposes of illustration, notlimitation. All of the variables with regard to quantity, location,orientation, etc. discussed previously may be implemented by varying thegeneric procedure described hereinafter.

The method illustrated in FIGS. 8A-8L is a percutaneous procedure inwhich access to the disc 50 is achieved utilizing a number of smalldiameter tools which may be inserted through a patient's back (skin andback muscles), between adjacent vertebrae, and into the patient's disc50. This percutaneous method minimizes the invasiveness of the procedurethereby reducing procedure time, procedure cost, postoperative pain andrecovery time.

Initially, as shown in FIG. 8A, the rigid trocar 410 is positioned forinsertion into the disc 50 as in a conventional discogram procedure. Therigid trocar 410 is advanced until the distal tip 413 of the trocar 410is proximate the outer periphery of the posterior portion of the annulus52 as seen in FIG. 8B.

The curved portion 426 of the semi-rigid needle 420 is straightened forinsertion into the trocar 410 as shown in FIG. 8C. The semi-rigid needle420 (alone or with stylet 430) is advanced relative to the rigid trocar410 until the curved portion 426 of the semi-rigid needle exits thedistal tip 413 of the rigid trocar 410 and the desired amount ofcurvature is established, as seen in FIG. 8D. The curved portion 426 maybe advanced until the tip 423 is roughly parallel to the posteriorcurvature of the annulus 52.

The sharpened stylet 430 is then positioned for insertion into thesemi-rigid needle 420 as shown in FIG. 8E. The sharpened stylet 430 isadvanced relative to the semi-rigid needle 420 until the distal tip 433of the stylet 430 extends across radial fissures 56, as shown in FIG.8F.

The semi-rigid curved needle 420 is removed from the stylet 430 andtrocar 410, and the reinforcement member 100 is positioned foradvancement over the stylet 430 as shown in FIG. 8G. The reinforcementmember 100 is advanced over the stylet 430 and into the trocar 410, andthe driver 440 is positioned for advancement over the stylet 430 asshown in FIG. 8H. The driver 440 is then rotated and advanced over thestylet 430 in order to rotate and push the reinforcement member 100 intothe annulus and across the radial fissures 56 as seen in FIG. 8I. If thereinforcement member 100 utilizes an anchor other than threads, thedriver 440 may be used to simply push or otherwise advance thereinforcement member 100 through the trocar 410 and into the annulus 52.

If a solid cross-section reinforcement member 100 is utilized, it is notnecessary to utilize the stylet 430. In this situation, the curvedsemi-rigid needle 420 is left in place as shown in FIG. 8E and the solidcross-section reinforcement member 100 is advanced therethrough. Thedriver 440 is then rotated and advanced through the curved semi-rigidneedle 420 in order to rotate and push the reinforcement member 100 intothe annulus 52 and across the radial fissures 56. In this alternativemethod, it may be necessary to resize the curved semi-rigid needle 420to accommodate the driver 440 and reinforcement member 100.

The variable pitch threads on the reinforcement member 100 compress thedisc 50 and cause the fissures 56 to close as discussed previously. Ifvariable pitch threads are not utilized on the reinforcement member 100,other techniques may be used to compress the disc 50 and close theradial fissures 56. An example of an alternative disc 50 compressiontechnique is a step-wise advancement and tension method. In thisalternative method, the distal tip 433 of the stylet 430 is incorporatedwith an anchor 435 such as threads. After the distal tip 433 of thestylet 430 has been advanced by rotation to extend across the fissures56, and before the reinforcement member 100 has been advanced into theannulus 52, the stylet is pulled in the proximal direction to applytension thereto. Because, the threaded anchor at the distal end 433 ofthe stylet 430 grips the annulus 52, tension applied to the stylet 430compresses a portion of the disc 50 and closes the fissures 56. Oncecompression of the disc 50 and closure of the fissures 56 areestablished, the reinforcement member 100 may be advanced into theannulus 52 to maintain disc 50 compression and hold the fissures 56closed. This method of step-wise advancement and tension may be repeateduntil the reinforcement member 100 is fully implanted in the desiredposition within the annulus 52.

After the reinforcement member 100 is positioned across the radialfissures 56 as shown in FIG. 8I, the stylet is advanced until the distaltip extends across the circumferential fissure 58 as shown in FIG. 8J.Note that the curvature 434 of the stylet 430 defines the insertion pathof the reinforcement member 100. It has been observed that the presetcurvature 434 of the stylet 430 will correspond to the insertion path ifthe tip 433 is very sharp. With the stylet 430 advanced such that thetip extends across fissure 58, the driver 440 is then used to rotate andadvance the reinforcement member 100 across the fissure 58 as shown inFIG. 8K. The variable pitch threads on the reinforcement member 100compress the disc 50 and cause the fissure 58 to close as discussedpreviously. Once the reinforcement member 100 is completely deployedwithin the annulus 52 as shown in FIG. 8L, the tools 410/430/440 may beremoved from the patient and the procedure is essentially complete.

With general reference to FIGS. 9A-9F, schematic illustrations ofadditional tools 450/460/720 for use in the method of implantingreinforcement member 200 are shown. The additional tools include avariable curvature stylet 450 as shown in FIG. 9A, a stiffening mandrel460 as shown in FIG. 9B, and an advancement tool 720 as shown in FIG.9D. The variable curvature stylet 450 is hollow which permits insertionof the stiffening mandrel 460 as shown in FIG. 9C.

As seen in FIG. 9A, the variable curvature stylet 450 includes a tubularshaft 452, a curved distal portion 454 and a closed distal end 453 whichis sharpened. The variable curvature stylet 450 is substantially thesame as the curved stylet 430 described previously, except for theprovision of a lumen into which the stiffening mandrel 460 isinsertable. As seen in FIG. 9B, the stiffening mandrel 460 includes anelongate shaft 462 and a blunt tip 463. The shaft 462 and tip 463 of thestiffening mandrel 460 are sized to be inserted into the hollow shaft452 of the stylet 450. The hollow stylet 450 and the stiffening mandrel460 may be made of stainless steel, nickel titanium alloy or the like.

As can be seen from a comparison of FIGS. 9A and 9C, upon insertion ofthe stiffening mandrel 460 into the hollow stylet 450, the curvatureincreases. Preferably the stiffening mandrel 460 is inserted fully intothe hollow stylet 450 to increase the radius of curvature of the distalportion of the curvature 454, since the distal portion of the curvature454 dictates the path that the stylet 450 will follow. The relativestiffness of the stylet 450 and stiffening mandrel 460 may be selectedto vary the amount of change in the curvature 454. The variablecurvature 454 may be used to navigate around the changing curvature ofthe annulus 52 as described hereinafter. At any point during advancementof the stylet 450, the curvature 454 may be adjusted by insertion of anappropriately stiff mandrel 460. The path defined by the stylet 450 maythus be customized to any particular disc 50 anatomy.

As seen in FIG. 9D, advancement tool 720 may be optionally employed todrive the distal end of the hollow stylet 450 through annular tissue 52.The advancement tool 720 includes an elongate tubular shaft 722, with ahandle 724 connected to its proximal end and a plurality of threads 726connected to its distal end. The tubular shaft 722 of the advancementtool 720 includes a lumen which is sized to accommodate the variablecurvature stylet 450 therein. To transfer forces from the distal end ofthe advancement tool 720 to the distal end of the stylet 450, thevariable curvature stylet 450 may include a tapered collar 456. Withthis arrangement, the advancement tool 720 may be advanced over thevariable curvature stylet 450 until the distal end of the shaft 722abuts the collar 456 on the variable curvature stylet 450. During use,the threads 726 engage the annular tissue 52 and upon rotation, applylongitudinal forces against the collar 456, and thereby cause distaladvancement of the variable curvature stylet 450. The threads 726 arerotated by manually rotating handle 724, which transmits torsionalforces along the elongate shaft 722 to the distal threads 726. Toprovide adequate transmission of torsional forces, the tubular shaft 722may further comprise a composite structure as illustrated in FIG. 9E ormetallic tubular structure as illustrated in FIG. 9F.

With specific reference to FIG. 9E, the tubular shaft 722 comprises acomposite structure having an outer layer 721 disposed about areinforcement layer 723 disposed about an inner layer 725. The outerlayer 721 and the inner layer 725 may comprise a polymeric materialhaving a relatively low coefficient of friction such as PTFE or HDPE.The reinforcement layer 723 is preferably torsionally rigid in bothdirections of rotation, as may be provided by an interwoven wire braidor by multiple wire coils wound in opposite directions.

With specific reference to FIG. 9F, the elongate tubular shaft 722comprises a tube 727 which may be formed of a highly elastic and rigidmetal such as stainless steel, nickel titanium alloy, or the like. Themetallic tube 727 includes a plurality of slots 729 spaced at regularincrements along the length of the shaft 722. The slots 729 extendthrough the wall of the metallic tube 727, but do not extend about theentire circumference of the metallic tube 727. Thus, the slots 729impart flexibility to the flexible tube 727, while maintaining torsionalrigidity thereof.

With general reference to FIGS. 10A-10H, the steps for implantingcircumferential reinforcement member 200 are illustrated. All of thevariables with regard to quantity, location, orientation, etc. discussedpreviously may be implemented varying the generic procedure describedhereinafter. The method illustrated in FIGS. 10A-10H is a percutaneousprocedure in which access to the disc 50 is achieved utilizing a numberof small diameter tools which may be inserted through a patient's back(skin and back muscles), between adjacent vertebrae, and into thepatient's disc 50.

Initially, as shown in FIG. 10A, the rigid trocar 410 is advanced intothe annulus 52 of the disc 50. The trocar 410 is advanced until thedistal tip 413 thereof is disposed in the lateral portion of the annulus52 roughly half way between the posterior and anterior portions of theannulus 52 as seen in FIG. 10B. The hollow curved stylet 450 with thestiffening mandrel 460 inserted therein is then advanced into the trocar410. Note that an appropriate stiff mandrel 460 has been fully insertedinto the hollow stylet 450 a sufficient distance to define a curvature454 that approximates the curvature of the anterior portion of theannulus 52. Continued advancement of the hollow stylet 450 andstiffening mandrel 460 as a unit cause the stylet 450 to traverse theanterior portion of the annulus 52 as shown in FIG. 10C.

After the distal tip 453 of the stylet 450 is positioned roughly halfway between the posterior and anterior portions of the annulus 52 asseen in FIG. 10C, the stiffening mandrel 460 is retracted or removedfrom the stylet 450 to define a smaller curvature 454 that approximatesthe curvature of the posterior lateral portion of the annulus 52. Thestylet 450 is then advanced until the distal tip 453 thereof enters theposterior portion of the annulus 52 as shown in FIG. 10D.

An appropriately stiff mandrel 460 is then advanced or inserted into thehollow stylet 450 to define a curvature 454 that approximates thecurvature of the posterior portion of the annulus 52. The stylet is thenadvanced across the posterior portion of the annulus 52. The stiffeningmandrel 460 is then retracted or removed from the stylet 450 to define asmaller curvature 454 that approximates the curvature of the posteriorlateral portion of the annulus 52. The stylet 450 is then advanced untilthe distal tip 453 thereof is positioned adjacent the distal tip 413 ofthe trocar 410 as shown in FIG. 10E.

The trocar 410 is then removed from the patient leaving the stylet 450in the annulus 52 to define the insertion path for the reinforcementmember 200 as shown in FIG. 10F. The circumferential reinforcementmember 200 and driver 440 are then advanced over the stylet 450 as shownin FIG. 10G. Using the driver 440 to push and rotate the circumferentialreinforcement member 200, the member 200 is advanced into the annulus 52along the path defined by the stylet 450 until the distal end of thereinforcement member 200 is adjacent the proximal end of thereinforcement member 200. Note that the variable pitch threads 222compress the disc 50 and cause the fissure 56/58 to close. If thereinforcement member 200 includes an anchor 220 other than threads(e.g., sloped rings, barbs, etc.) the driver 440 may be used to simplypush the reinforcement member 200 into the annulus 52. Once thereinforcement member 200 is in the desired position, the driver 440 andstylet 450 may be removed from the patient to complete the procedure.

With general reference to FIGS. 11A-11H, the steps for implantingreinforcement member 300 are illustrated. All of the variables withregard to quantity, location, orientation, etc. discussed previously maybe implemented by varying the generic procedure described hereinafter.The method illustrated in FIGS. 11A-11H is a percutaneous procedure inwhich access to the disc 50 is achieved utilizing a number of smalldiameter tools which may be inserted through a patient's back (skin andback muscles), between adjacent vertebrae, and into the patient's disc50.

Initially, as shown in FIG. 11A, two trocars 410 are positioned forinsertion into the disc 50. The trocars 410 are advanced until thedistal tip 413 of each trocar 410 is proximate the outer periphery ofthe posterior portion of the annulus 52 as seen in FIG. 11B. The curvedstylet 430 is then advanced into one of the trocars 410 and advancedinto the annulus 52 as shown in FIG. 11C. The curved stylet 430 is thenadvanced across the posterior annulus 52, into the distal tip 413 of theother trocar 410, and out the proximal end of the other trocar 410 asshown in FIG. 11D. The curvature 434 of the stylet 430 is selected suchthat the tip 433 of the stylet 430 traverses the posterior portion ofthe annulus 52 and automatically enters into the other trocar 410. Tofacilitate automatic insertion of the stylet into the other trocar 410,the inside diameter of the trocar 410 may be tapered to increase theinside diameter closer to the tip 413. As mentioned previously, thestylet 430 will follow a path in the annulus 52 corresponding to thecurvature 434 of the stylet 430 if the tip 433 is very sharp.

The trocars 410 are then removed from the patient leaving the stylet 430in place as shown in FIG. 11E. Also as shown in FIG. 11E, the screws 320are placed in the holes 334 of the connection rings 330, and theconnection rings 330 are slid onto the stylet 430 through holes 332. Thescrews 320 are then screwed into the annulus 52 as shown in FIG. 11Fusing a conventional driver (not shown). Placing the screws 320 in thelateral portions of the annulus 52 takes advantage of the generallygreater integrity (usually thicker and healthier) of the lateralportions of the annulus 52 to establish firm anchor points.

Also as shown in FIG. 11F, the tubular pins 310 are positioned on thestylet 430. The tubular pins 310 are then advanced over the stylet 430,across the posterior portion of the annulus 52, and screwed together asshown in FIG. 11G using driver 440 (not shown). The pins 310 are have anassembled length which is shorter than the length of the stylettraversing the annulus 52 such that connection of the pins 310 causescompression of the disc 50 and closure of the fissures 56/58. Afterremoval of the stylet 430, the screws 320 may be tightened further intothe annulus 52 in order to further compress the disc 50 and close thefissures 56/58 as shown in FIG. 11H.

With general reference to FIGS. 12A-12G, FIGS. 13-15, FIGS. 16A-16E, andFIGS. 17A-17D, schematic illustrations of additional tools710/730/740/750/800/900 are shown for use in implanting reinforcementmember 600 in accordance with the method illustrated in FIGS. 18A-18L.The additional tools include a curved stylet or needle 710 as shownFIGS. 12A-12G, a guide tube or sheath 730 as shown in FIG. 13, a pledgetpush rod 740 as shown in FIG. 14, a pledget 750 as shown in FIGS. 14 and15, a column support and advancement device 800 for stylet 710 as shownin FIGS. 16A-16E, and a column support and advancement device 900 forstylet 710 and sheath 730 as shown in FIGS. 17A-17D. Tools710/730/800/900 and the associated method may be utilized to implantother reinforcement members described herein, including reinforcementmembers 100/200/300.

With specific reference to FIGS. 12A-12G, the stylet or needle 710includes a flexible elongate shaft 711 and a sharpened distal end 714.The stylet 710 is similar to the curved stylet 430 described withreference to FIG. 7C, except as described herein and apparent from thedrawings. The stylet or needle 710 may have a substantially straightdistal portion 712A as shown in FIG. 12A. Alternatively, the stylet 710may be curved as illustrated in FIGS. 12B-12E.

For example, in FIG. 12A, the stylet 710A includes a straight distalportion 712A. In FIG. 12B, the stylet 710B includes a curved portion712B having a curvature that may, for example, correspond to theanterior curvature of the annulus 52. In FIG. 12C, the stylet 710Cincludes a curved portion 712C having a curvature that may, for example,correspond to the curvature of the lateral portions of the annulus 52.In FIG. 12D, the stylet 710D includes a distal curved portion 712Dhaving a curvature that permits relatively sharp turns or counter-turnsduring navigation through the annulus 52. In FIG. 12E, the stylet 710Ehas a primary curvature 712E and a secondary opposite curvature 716Eproximal thereon. The provision of a primary curvature 712E in additionto a secondary opposite curvature 716E allows the stylet 710E to changedirections during navigation within the annulus 52. To this end, thesecondary curvature 716E may have a curvature corresponding to the pathalready defined through the annulus 52 during navigation, and theprimary curvature 712E may have a curvature corresponding to the path tobe taken by the stylet 710E upon further advancement through the annulus52. Although a limited number of distal configurations 712 have beenillustrated, it is contemplated that a variety of stylets 710 having avariety of distal geometries 712 may be employed during the implantationprocedures described hereinafter.

The shaft 711 of the stylet 710 preferably has a flexible but pushableconstruction incorporating a rigid metal mandrel such as stainlesssteel, or a super-elastic alloy such as nickel-titanium. Highly elasticor super-elastic materials incorporated into the elongate shaft 711resist permanent deformation during insertion and navigation through theannulus 52. The shaft 711 of the stylet 710 may have a diameter rangingfrom 0.010 to 0.025 inches, which may vary depending on the tortuosityof the annular path and the characteristics (toughness, friction) of theannular material 52. The shaft 711 may be coated with a lubriciousmaterial such as PTFE and a hydrophilic polymer.

It has been found that if the tip 714 is sufficiently sharp to easilypenetrate annular tissue 52, the path through the annular tissue 52taken by the stylet 710 will substantially conform to the geometry ofthe distal portion 712 of the stylet 710. In particular, if the distalportion 712 is substantially straight, the stylet 710 will define alinear path through the annular tissue 52. Alternatively, if the distalportion 712 has a curve or other nonlinear geometry (in a relaxedstate), the stylet 710 will define a path through the annular tissue 52corresponding to the shape of the distal portion 712. To this end, it isdesirable to provide a tip 714 having sufficient sharpness to readilypenetrate annular tissue 52, which tends to be relatively fibrous andtough. The distal tip 714 may have a symmetrical geometry 714A asillustrated in FIG. 12F or an asymmetrical geometry 714B as illustratedin FIG. 12G, and preferably has a fine to micro-fine sharpness. Byproviding a sufficiently sharp tip 714, navigation through the annulus52 may be performed in a predictable manner as described in more detailhereinafter.

With specific reference to FIG. 13, the guide tube or sheath 730includes an elongate tubular shaft 732 having a lumen extendingtherethrough sized to accommodate the stylet 710. The guide tube orsheath 730 preferably has a relatively thin wall structure so as tominimize the increase in profile relative to the stylet 710. Inaddition, the inside surface of the shaft 732 preferably has a lowfriction coating or liner such as PTFE to minimize friction between theguide sheath 730 and the stylet 710. The guide sheath 730 preferably isable to withstand relatively high longitudinal compressive forces andtherefore, preferably comprises a relatively rigid but flexible materialsuch as PTFE or polyimide. For example, the tubular shaft 732 maycomprise a polyimide tube having an inside diameter approximately 0.0005to 0.001 inches greater than the outside diameter of the stylet 710,with a wall thickness of approximately 0.0005 to 0.003 inches. Thetubular shaft 732 may further incorporate a reinforcement layer such asa metallic braid or the like to help prevent various modes of buckling.

With specific reference to FIG. 14, the pledget push rod 740 includes anelongate rigid shaft 742 comprising, for example, a stainless steel rod.The distal end of the shaft 742 is connected to pledget 750 by way of areleasable connection 744. Releasable connection 744 may comprise, forexample, a weakened area of the rod 742 or pledget 750 that may bebroken by application of torsional forces to the rod 742.

With specific reference to FIG. 15, the pledget 750 includes a bodyportion 752 and two holes 754 sized to accommodate the stylet 710 andreinforcement member 600. The body portion 752 may comprise a metallicor polymeric material. Examples of suitable metallic materials includestainless steel and super-elastic alloys such as nickel-titanium. If thebody portion 752 comprises a polymeric material, the polymeric materialmay be biologically inert, biodegradable or bioabsorbable. Examples ofsuitable polymeric materials comprising biologically stable or inertmaterials include HDPE and PTFE. Examples of biodegradable orbioabsorbable materials include resorbable collagen, LPLA(poly(1-lactide)), DLPLA (poly(d1-lactide)), LPLA-DLPLA, PGA(polyglycolide), PGA-LPLA or PGA-DLPLA. The body portion 752 of thepledget 750 may be coated with biocompatible materials, growth factorsto facilitate healing, agents which render the nuclear matter inert orotherwise reduce chemical irritation thereof, and/or anesthetic agentsto reduce nerve signal transmission (i.e., pain).

With specific reference to FIGS. 16A-16E, the column support andadvancement device 800 for use with stylet 710 is shown. Device 810includes a shaft portion 810 which extends through and is rigidlyconnected to a proximal handle assembly 812. The distal end of the shaft810 may incorporate a plurality of threads 814 to rotationally engageand bore through tissues in the back (dermal and muscular tissues) andanchor against tissues immediately adjacent the point of entry into theannulus 52. The distal tip 815 of the shaft 810 may also be sharpened tofacilitate penetration through tissues in the back. The shaft 810comprises a rigid metal tube having a lumen extending therethroughadapted to receive the stylet 710. The inside surface of the tubularshaft 810 may be provided with a low friction liner or coating such asPTFE. Within the handle 812, the shaft 810 includes a slot aligned witha slot or keyway 816 in the handle 812, which is sized and shaped toaccommodate key 820. The slot in the shaft 810 contained within thehandle assembly 812 has a width that is less than that of the outsidediameter of the stylet 710 such that the stylet 710 cannot passtherethrough and such that the shaft 810 provides column support to thestylet 710 and prohibits buckling thereof.

Key 820 includes a thumb button 822 which may incorporate a plurality ofgrip members 828. A metallic plate 824 extends downwardly from the bodyportion 822 and has a geometry which substantially conforms to keyway816. The bottom of the plate 824 incorporates one or more protrusions826. Protrusions 826 engage and mate with recesses 715 formed in theproximal end of the stylet 710. Protrusions 826 and recesses 715 may bereplaced by a wide variety of mating geometries to facilitate engagementbetween the key 820 and the proximal end of the stylet 710.

Upon depression of the thumb button 822 relative to the handle 812, theplate 824 travels in a downward direction to force the protrusions 826into the recesses 715. The thumb button 822 may then be advanced in thedistal direction, while maintaining downward pressure, to advance thestylet 710 in the distal direction relative to the shaft 810 intoannular tissue 52. Although the stylet 710 may encounter substantialresistance during advancement through annular tissue 52, and despite therelative flexibility of the stylet 710, the shaft 810 of the advancementdevice 800 provides sufficient column strength to the stylet 710 toresist buckling during advancement.

After the key 820 has been advanced to the distal end of the handle 812,the downward force applied to the thumb button 822 may be removed todisengage the protrusions 826 from the recesses 715 in the stylet 710.To facilitate disengagement of the teeth 826 from the recesses 715, apair of leaf springs 825 may be provided on either side of the plate 824to urge the key 820 in the upward direction relative to the handle 812.In the disengaged position, the key 820 may be moved to the proximal endof the handle 812, and a downward force may be reapplied to the thumbbutton 822 to cause engagement of the protrusions 826 with the recesses715. The thumb button 822 may then be advanced again in the distaldirection relative to the handle 812 to advance the stylet 710 furtherinto the annular tissue 52.

This procedure may be repeated until the stylet 710 is advanced thedesired distance. In addition, with the key 820 in the disengagedposition, the stylet 710 may be removed for a different stylet 710having a different distal curvature, for example. To exchange the stylet710, downward pressure against the thumb button 822 is removed to allowthe key 820 to be urged in the upward direction by springs 825, tothereby disengage the protrusions 826 from the recesses 715. In thedisengaged position, the stylet 710 may be removed from the device 800by pulling the stylet 710 in the proximal direction. A second stylet 710may be inserted into the device 800 by inserting the distal end of thestylet 710 into the proximal end of the lumen of the shaft 810 locatedat the proximal end of the handle assembly 812. The stylet may then beadvanced until the distal end thereof exits the distal end of the shaft810.

With specific reference to FIGS. 17A-17D, column support and advancementdevice 900 for use with stylet 710 and sheath 730 is shown. Device 900includes a rigid metallic tubular shaft 910 having a handle 912connected to its proximal end. A plurality of threads 914 are providedat the distal end of the shaft 910 to facilitate advancement throughtissues up to the perimeter of the annulus 52, and to facilitateanchoring of the tubular shaft 910 adjacent the periphery of the annulus52. The distal tip 915 of the tubular shaft 910 is sharpened tofacilitate advancement through dermal and muscular tissues in the backup to and adjacent the annulus 52. The tubular shaft 910 has an insidediameter sized to accommodate the guide sheath 730 which is sized toaccommodate the stylet 710. The inside diameter of the tubular shaft 910may incorporate a low friction coating such as PTFE to minimize frictionbetween the tubular shaft 910 and the tubular sheath 730.

The tubular shaft 910 includes a helical slot 916 which passes throughthe wall thereof and extends from a point adjacent the handle 912 to amid portion of the shaft 910. A proximal nut 920 and a distal nut 930are disposed about the shaft 910 and cooperate with the helical slot 916such that they may be independently longitudinally advanced andretracted by rotation thereof relative to the shaft 910.

As best seen in FIG. 17B, the proximal nut 920 abuts a collar 918fixedly connected to the stylet 710. Similarly, the distal nut 930 abutsa collar 732 fixedly attached to the tubular sheath 730. Thus,longitudinal advancement of nut 920 by rotation thereof relative to theshaft 910 causes corresponding longitudinal advancement of the stylet710. Similarly, longitudinal advancement of nut 930 by rotation thereofrelative to shaft 910 causes corresponding longitudinal advancement ofthe tubular sheath 730.

As seen in FIG. 17C, proximal nut 920 includes a collar 924 connected toa bearing 926 by a pair of arms 922. The arms 922 extend through thehelical slot 916 in the shaft 910. The collar 924 extends around theoutside of the shaft 910, and the bearing 926 fits within the lumen ofthe shaft 910. The bearing 926 has an inside diameter sized toaccommodate the stylet 710 in an outside diameter sufficient to engageand abut the collar 718, while permitting relative rotational movement.The side openings 928 in the collar 924 and bearing 926 permit theproximal nut 920 to be removed from the shaft 910, which in turn permitsthe stylet 710 to be removed from the device 900 and replaced with adifferent stylet 710 having a different distal curvature, for example.

As seen in FIG. 17D, the distal nut 730 includes a collar 934 connectedto a bearing 936 by a pair of arms 932. The collar 934 has an insidediameter sufficient to accommodate the outside diameter of the shaft910. The bearing 936 has an outside diameter sized to fit within thelumen of the shaft 910 and sized to engage and abut the collar 732 onthe tubular sheath 730. The bearing 936 also has an inside diametersufficient to accommodate the tubular sheath 730, while allowingrelative rotational movement.

With this arrangement, the stylet 710 may be advanced independently ofthe sheath 730, and visa-versa. In addition, with this arrangement, boththe tubular sheath 730 and the stylet 710 have column support proximalof the path being navigated through the annulus 52.

With general reference to FIGS. 18A-18L, the steps for implantingreinforcement member 600 are illustrated. The method illustrated inFIGS. 18A-18L utilizes stylet 710 to navigate through the annulus 52 andimplant reinforcement member 600. The method illustrated in FIGS.18A-18L may be modified to make use of hollow stylet 450 and stiffeningmandrel 460 to navigate through the annulus 52 and implant reinforcementmember 600. All of the variables with regard to quantity, location,orientation, etc., discussed previously may be implemented by varyingthe generic procedure described hereinafter. The method illustrated inFIGS. 18A-18L is a percutaneous procedure in which access to the disc 50is achieved utilizing a number of small diameter tools which may beinserted through a patient's back (skin and back muscles), betweenadjacent vertebrae, and adjacent the patient's disc 50.

Initially, as shown in FIG. 18A, the rigid trocar 410 is advanced untilthe distal tip thereof is disposed immediately adjacent the periphery ofthe annulus 52 of the disc 50. A stylet 710C, with tubular sheath 730disposed thereon, is inserted into the rigid trocar 410. The stylet710C, having a curved distal portion 712C, is advanced out the distalend of the trocar 410 into the annulus 52 until the distal end of thestylet 710C is located in the anterior portion of the annulus 52 asshown in FIG. 18B. Note that the curvature of the distal portion 712Croughly corresponds to the curvature of the lateral annulus 52. Thesheath 730 may then be advanced over the stylet 710C until the distalend of the sheath is adjacent the distal end of the stylet 710.

The stylet 710C may then be removed from the sheath 730, and anotherstylet 710B, having a curved distal portion 712B, may be advancedthrough the sheath 730 as shown in FIG. 18C. In this manner, the tubularsheath 730 maintains the path defined by the penetrating stylet 710C,and allows the next stylet 710B to begin penetration where stylet 710Cleft off. The stylet 710B is advanced until the distal tip is positionedin the lateral portion of the annulus, after which the tubular sheath730 may be advanced thereover. Note that the curvature of the distalportion 712B roughly corresponds to the curvatures of the anteriorannulus 52. The stylet 710B may be exchanged for stylet 710C having acurved portion 712C to traverse the lateral side of the annulus 52. Thestylet 710C may then be exchanged for another stylet 710A having arelatively straight distal portion 712A to traverse the posteriorportion of the annulus 52 as shown in FIG. 18D. The tubular sheath 730is then advanced over the stylet 710A until the distal end of the sheath730 is adjacent the distal end of the stylet 710A.

Once the distal end of the stylet 710A and the distal end of the tubularsheath 730 are disposed adjacent the opening to the distal end of thetrocar 410, the straight stylet 710A may be exchanged for double curvestylet 710E as shown in FIG. 18E. The distal tip of the stylet 710E isnavigated into the distal end of the trocar 410 utilizing thevisualization techniques described previously. Once the distal end ofthe stylet 710 is disposed in the trocar 410, the tubular sheath 730 maybe removed. With the distal end of the stylet 710E reentered into thedistal end of the trocar 410, the stylet 71 0E may be freely advanceduntil the distal portion thereof exits the proximal portion of thetrocar 410 as shown in FIG. 18F.

At this point, the trocar 410 may also be removed, but may optionally beleft in place, depending on the means employed to connect the ends ofthe reinforcement member 600. As illustrated in FIG. 18G, one end 602 ofthe reinforcement member 600 is connected to the proximal end of thestylet 710. This may be accomplished, for example, by threading thereinforcement member through a hole (not shown) in the proximal end ofthe stylet 710 similar to the threading a sewing needle. Immediatelybefore or immediately after the reinforcement member 600 is attached tothe proximal end of the stylet 710, the pledget push rod 740 may be usedto push the pledget 750 over the opposite ends of the stylet 710 untilthe pledget 750 is positioned immediately adjacent the entry and exitpoints in the annulus 52 as illustrated in FIG. 18G.

The distal end of the stylet 710 may then be pulled while applying apush force to the push rod 740 to pull the reinforcement member alongthe path defined the stylet 710 through the annulus 52, after which thereinforcement member 600 may be disconnected from the stylet as shown inFIG. 18H. A connection (e.g., knot) 610 may be made in the reinforcementmember 600 and advanced to the pledget 750 utilizing a conventional knotpusher (not shown) as shown in FIG. 181. While the knot is beingtightened, the reinforcement member 600 applies compressive forces aboutthe perimeter of the annulus 52 thereby closing fractures and fissures56/58. Once the knot 610 has been tightened, the reinforcement member600 may be cut immediately proximal of the knot 610 adjacent the pledget750 as shown in FIG. 18J utilizing a conventional suture cutting device(not shown).

Alternatively, as shown in FIGS. 18K and 18L, the pledget 750 may beomitted. In particular, a connection (e.g., knot) 610 may be made in thereinforcement member 600 and advanced to the entry and exit point in theannulus 52 utilizing a conventional knot pusher (not shown) as shown inFIG. 18K. While the knot is being tightened, the reinforcement member600 applies compressive forces about the perimeter of the annulus 52thereby closing fractures and fissures 56/58. Once the knot 610 has beentightened, the reinforcement member may be cut utilizing a conventionalsuture cutting device (not shown) immediately proximal of the knot 610as shown in FIG. 18L.

The path navigated through the annulus 52 by the foregoing method may bea function of the individual anatomical geometry of the patient and/orthe particular portion of the annulus 52 requiring compression.Accordingly, as shown in FIGS. 19A-19F, the path 620 defined by thestylet 710 and reinforcement member 600 through the annulus 52 may vary.For example, a substantial rectangular path 620A with rounded cornersmay be employed as illustrated in FIG. 19A. Alternatively, asubstantially trapezoidal path 620B having rounded comers may beemployed as shown in FIG. 19B. Alternatively, a substantially oval path620C may be employed as shown in FIG. 19C. Each of these paths may bedefined by the particular sequence of curved stylets 710 utilized inaccordance with the method described previously.

Although it is preferable to define a path 620 substantially confined tothe annulus 52, the path 620 may also extend through a portion of thenucleus 54 as illustrated in FIGS. 19D and 19E. In such circumstances,it is preferable to not define a direct path from the nucleus 54 to theexterior of the annulus 52, to thereby minimize the likelihood thatnuclear material will leak out of the disc 50. For example, as shown inFIG. 19D, the path through the nucleus 54 may enter at one lateral side,and exit at the opposite lateral side thereof. Alternatively, as shownin FIG. 19E, the path 620E may enter on the anterior side and exit onthe posterior side of the nucleus 54. FIG. 19F illustrates a path 620Fwhich is just external to the outer surface of the annulus 52.

While a single path 620 followed by a single reinforcement member 600 isillustrated, it is also contemplated that multiple reinforcement members600 may be implanted. For example, one reinforcement member 600 could beimplanted proximate the lower (inferior) portion of the annulus52 andone reinforcement member 600 could be implanted in the upper (superior)portion of the annulus 52. Any number of reinforcement members 600 couldbe implanted in a single disc, either through a single trocar 410placement, or multiple trocar placements.

With general reference to FIGS. 20A-20R, alternative embodiments ofreinforcement members and methods of implantation are disclosed. Thereinforcement members 510/520/530 may be used to reinforce the disc,restore disc height and/or bear some or all of the load normally carriedby the annulus. The reinforcement members 510/520/530 are relativelyrigid and thus serve to reinforce the disc 50, and particularly theannulus 52, where inserted. In addition, the reinforcement members510/520/530 may have a relatively large profile when implanted and thusincrease disc height.

The reinforcing members 510/520/530 may be used singularly or in groups,depending on the increase in disc 50 height desired and/or the amount ofreinforcement of the annulus 52 desired. For example, the reinforcingmembers 510/520/530 may be stacked or inserted side-by-side. Inaddition, the reinforcing members 510/520/530 may be located invirtually any portion of the annulus 52. Preferably, the reinforcingmembers 510/520/530 are substantially symmetrically disposed about themedian plane 70 to avoid causing curvature of the spine 10. Although thereinforcing members 510/520/530 may be inserted, in part or in whole,into the nucleus 54, it is preferable to insert them into the annulus 52for purposes of stability and load carrying. Specifically, to providestability, it is desirable to symmetrically locate the reinforcingmembers 510/520/530 as far as reasonably possible from the median plane70, or to span as great a distance as possible across the median plane70. In addition, because the annulus 52 of the disc 50 is believed tocarry the majority of the load, particularly in the lumbar region 12,the reinforcing members 510/520/530 are preferably placed in the annulus52 to assume the load normally carried thereby, and reinforce the loadbearing capacity of the annulus 52, without hindering the normalmobility function of the disc 50.

The reinforcing members 510/520/530 may comprise expandable members suchas self-expanding members 510 or inflatable members 520. Alternatively,the reinforcing members 510/520/530 may comprise unexpandable memberssuch as reinforcement bars 530. When implanting each type ofreinforcement member 510/520/530, it is preferable to maintain theintegrity of the annulus 52. Accordingly, space in the annulus 52 forthe reinforcing members 510/520/530 is preferably established bydilation or the like, although some amount of tissue removal may beused.

The expandable reinforcement members 510/520 are useful because they maybe delivered in a low profile, unexpanded condition making it easier totraverse the very tough and fibrous collagen tissue of the annulus 52.For similar reasons, the reinforcement bars 530 are useful because theymay have a small diameter and a sharpened tip. Although it is possibleto insert the expandable reinforcing members 510/520 into the annulus 52in their final expanded state, it is desirable to deliver the expandablereinforcing members 510/520 into the annulus 52 in an unexpanded stateand subsequently expand them in order to minimize invasiveness andresistance to insertion.

The self-expanding reinforcing member 510 may comprise a solid orsemi-solid member that self-expands (e.g., by hydration) after insertioninto the annulus. Examples of suitable materials for such solid orsemi-solid members include solid fibrous collagen or other suitable hardhydrophilic biocompatible material. If the selected material isdegradable, the material may induce the formation of fibrous scar tissuewhich is favorable. If non-degradable material is selected, the materialmust be rigid and bio-inert. The self-expanding reinforcing member 510preferably has an initial diameter that is minimized, but may be in therange of 25% to 75% of the final expanded diameter, which may be in therange of 0.3 to 0.75 cm, or 10% to 75% of the nominal disc height. Thelength of the self-expanding member 510 may be in the range of 1.0 to6.0 cm, and preferably in the range of 2.0 to 4.0 cm.

The inflatable reinforcing member 520 may comprise an expandable hollowmembrane capable of inflation after insertion into the annulus. Anexample of a suitable inflatable structure is detachable balloonmembrane filled with a curable material. The membrane may consist of abiocompatible and bio-inert polymer material, such as polyurethane,silicone, or polycarbonate-polyurethane (e.g., Corethane). The curablefiller material may consist of a curable silicone or polyurethane. Thefiller material may be curable by chemical reaction (e.g., moisture),photo-activation (e.g., UV light) or the like. The cure time ispreferably sufficiently long to enable activation just prior toinsertion (i.e., outside the body) and permit sufficient time fornavigation and positioning of the member 520 in the disc. However,activation may also take place inside the body after implantation. Theinflatable reinforcing member 520 preferably has an initial deflateddiameter that is minimized, but may be in the range of 25% to 75% of thefinal inflated diameter, which may be in the range of 0.3 to 0.75 cm, or10% to 75% of the nominal disc height. The length of the inflatablemember 520 may be in the range of 1.0 to 6.0 cm, and preferably in therange of 2.0 to 4.0 cm.

The reinforcement bars 530 may comprise a rigid, solid or hollow barhaving a sharpened tip. The reinforcement bars 530 may comprisesstainless steel mandrels, for example, having a diameter in the range of0.005 to 0.100 inches, preferably in the range of 0.010 to 0.050 inches,and most preferably in the range of 0.020 to 0.040 inches, and a lengthin the range of 1.0 to 6.0 cm, and preferably in the range of 2.0 to 4.0cm. The reinforcement bars 530 may be straight for linear insertion, orcurved to gently wrap with the curvature of the annulus duringinsertion. In addition, the outer surface of the reinforcement bars 530may have circular ridges or the like that the permit easy insertion intothe annulus 52 but resist withdrawal and motion in the annulus followingimplantation. Other suitable materials for reinforcement bars 530include titanium alloy 6-4, MP35N alloy, or super-elasticnickel-titanium alloy.

With general reference to FIGS. 20A-20J, the steps for implanting aself-expanding reinforcement member 510 are illustrated. It should beunderstood that the procedure for implanting a single member 510 in theanterior annulus 52 is shown for purposes of illustration, notlimitation. All of the variables with regard to quantity, location,orientation, etc. discussed previously may be implemented by varying thegeneric procedure described hereinafter.

Initially, the sharpened stylet 430; semi-rigid needle 420 and rigidtrocar 410 are assembled. As shown in FIG. 20A, the distal portion ofthe assembly 410/420/430 is inserted into the disc 50 as in aconventional discogram procedure. The assembly 410/420/430 is advanceduntil the distal tip 413 of the rigid needle is proximate the anteriorcurvature of the annulus 52, near the anterior side of the nucleus 54,as seen in FIG. 20B. The semi-rigid needle 420 (alone or with stylet430) is advanced relative to the rigid trocar 410 until the curvedportion 426 of the semi-rigid needle exits the distal tip 413 of therigid trocar 410 and the desired amount of curvature is established, asseen in FIG. 20C. The curved portion 426 may be advanced until the tip423 is substantially parallel to the tangent of the anterior annulus 52curvature. The sharpened stylet 43Q is advanced relative to thesemi-rigid needle 420 to the desired position within the anteriorannulus 52, as shown in FIG. 20D. The semi-rigid needle 420 and therigid trocar 410 are completely withdrawn from the stylet 430, leavingthe stylet in position as shown in FIG. 20E.

A flexible dilator 470 is advanced over the stylet 430 to dilate theannulus 52, as seen in FIG. 20F. The flexible dilator 470 is similar tosemi-rigid needle 420 except that the dilator includes a blunt distaltip and is relatively more flexible, and has larger inner and outerdiameters. Note that one or more dilators 470 may be advanced co-axiallyabout the stylet 430 until the annulus is sufficiently dilated to acceptthe self-expandable member 510. The stylet 430 is then withdrawn fromthe flexible dilator 470 and the self-expandable member 510 isintroduced into the lumen of the flexible dilator 470 using a push bar480, as shown in FIG. 20G. Alternatively, the dilator 470 may be removedin favor of a flexible hollow catheter with a large inner diameter tofacilitate delivery of member 5 10. The push bar 480 is similar tostylet 430 except that the distal tip of the push bar 480 is blunt.Alternatively, the push bar 480 may simply comprise the stylet 430turned around, thus using the proximal blunt end of the stylet 430 asthe push bar 480. The push bar 480 is advanced until the member 5 10 isin the desired position, as seen in FIG. 20H. To facilitate positioningthe member 510, radiographic visualization may be used to visualize thedistal end of the push bar 480, which is formed of radiopaque materialand may include radiopaque markers. In addition, the member may beloaded with a radiopaque material to facilitate radiographicvisualization thereof.

After the member 510 is in the desired position, the flexible dilator470 is retracted from the push bar 480 while maintaining position of themember 510 with the push bar. The push bar 480 is then removed leavingthe member 510 in place. If necessary, the procedure may be repeated foradditional member implants 510. The member 510 is then allowed to expandover time, perhaps augmented by placing the spine 10 in traction.Alternatively, the spine 10 may be placed in traction prior to beginningthe procedure.

With reference to FIGS. 20K-20L, the steps for implanting an inflatablereinforcement member 520 are illustrated. In this procedure, the stepsoutlined with reference to FIGS. 20A-20F are followed. Specifically, thesame steps are followed up to and including the step of advancing theflexible dilator 470 over the stylet 430 to dilate the annulus 52, andthereafter removing the stylet 430 from the flexible dilator 470. Usinga catheter 490, the inflatable member 520 is introduced into the dilator470 and advanced until the member 520 is in the desired position, asshown in FIG. 20K. The inflatable member 520 is connected to the distalend of the catheter 490, which includes a flexible but pushable shaft492 and an inflation port 494. The flexible dilator 470 is retractedfrom the catheter 490 while maintaining position of the member 520.

With the member 520 in the desired position, which may be confirmedusing radiographic visualization as described above, the proximalinflation port 494 is connected to a syringe (not shown) or othersuitable inflation apparatus for injection of the curable fillermaterial. The filler material is then activated and the desired volumeis injected into the catheter 490 via the inflation port 494, as seen ifFIG. 20L. The filler material is allowed to cure and the catheter 490 isgently torqued to break the catheter 490 from the solid member 520. Thisbreak-away step may be facilitated by an area of weakness at thejuncture between the distal end of the catheter 490 and the proximal endof the member 520. The catheter 490 is then removed leaving the member520 in place. If necessary, the procedure may be repeated for additionalmember implants 520.

With reference to FIGS. 20M-20R, the steps for implanting areinforcement bar 530 are illustrated. As seen in FIG. 20M, the disc 50includes a protrusion or bulge 60, which is preferably, but notnecessarily, reduced or eliminated before insertion of the reinforcementbar 530. This may be done by separating the adjacent vertebrae 20. Inorder to establish separation of the vertebrae 20, the spine 10 may beplaced in traction or conventional intervertebral separation tools maybe used. After the bulge 60 is reduced or eliminated, similar steps arefollowed as outlined with reference to FIGS. 20A-20C.

Delivery of a single reinforcement bar 530 into the posterior annulus 52is illustrated. Specifically, the distal portion of the assembly410/420/480 is inserted into the disc 50 as in a conventional discogramprocedure. The assembly 410/420/480 is advanced until the distal tip 413of the rigid trocar 410 just penetrates the posterior side of theannulus 52, as seen in FIG. 20N. The semi-rigid needle 420 (alone orwith bar 530) is advanced relative to the rigid trocar 410 until thecurved portion 426 of the semi-rigid needle 420 exits the distal tip 413of the rigid trocar 410 and the desired amount of curvature isestablished, as shown in FIG. 20N. The curved portion 426 may beadvanced until the tip 423 is substantially parallel to the posteriorannulus 52.

Using the push bar 480, the reinforcement bar 530 with its sharpened tipis pushed into the annulus 52 as seen in FIG. 200. The reinforcement bar530 is advanced into the annulus 52 with the push bar 480 until the bar530 is in the desired position, as seen in FIG. 20P, which may beconfirmed using radiographic visualization as described above. The pushbar 480 is then retracted, leaving the reinforcement bar 530 in place,as shown in FIG. 20P. The semi-rigid needle 420 and the rigid trocar 410are then removed, as shown in FIG. 20Q, or, if necessary, the proceduremay be repeated for additional reinforcement bar implants 530, as shownin FIG. 20R. Presence of the reinforcement bars 530 serves to keep thedisc 50, and particularly the bulge 60, in a more normal condition, andto protect against continued bulging, thus easing nerve impingement.

With reference to FIGS. 21A-21C, an alternative reinforcement member 540is illustrated. In this embodiment, reinforcement member 540 includes ananchor arm 542 having an anchor mechanism 544 attached to a distal endthereof. The anchor mechanism 54 may comprise circular ridges, barbs orthe like which are readily advanced into the annular tissue 52, butresist retraction. Reinforcement member 540 also includes a lever arm546 including a distal sharpened tip 548. The distal end of the anchorarm 542 also incorporates a sharpened tip 548. The reinforcement member540 preferably comprises a highly elastic or super-elastic metal such asstainless steel or a nickel titanium alloy.

FIG. 21A illustrates the reinforcement member in a relaxed state, andFIG. 21B illustrates the reinforcement member in a compressed deliverystate sized to fit within trocar 410. The reinforcement member 540 maybe delivered into the annulus 52 in a compressed state through trocar410 utilizing push rod 480 as shown in FIG. 21C. As the reinforcementmember 540 is pushed out the distal end of the trocar 410 utilizing pushrod 480, the sharpened ends 548 penetrate the tissue and the anchormechanism 544 engages the tissue to define the deployed configurationshown in FIG. 21C. In the deployed configuration, the anchor arm and thelever arm are forced to pivot relative to each other thereby building abias force at the elbow connecting the anchor arm 542 and the lever arm546. In the deployed configuration, the lever arm 546 applies acompressive force to the exterior portion of the annulus 52 to minimizeprotrusions and bulges along the posterior periphery of the annulus 52.

With reference now to FIGS. 22A-22D, alternative reinforcement members570 and 580 are illustrated. Reinforcement members 570 and 580 aresimilar to reinforcement 600 except for the provision of distal anchors574/584. Except as described herein and apparent from the drawings, thefunction and delivery of reinforcement members 570 and 580 aresubstantially the same as reinforcement member 600.

As shown in FIG. 22A, reinforcement member 570 comprises a monofilamentor multifilament structure 572 that is highly flexible and has a hightensile strength. The ends of the filament structure 572 incorporateanchors 574, which may comprise circular ridges, barbs or the like whichare readily advanced into the annular tissue 52, but resist retraction.As shown in FIG. 22B, the reinforcement member 570 may be deployed inthe annulus 52 with the anchors residing in healthy annular tissue andthe filament structure partially surrounding the fractures and fissures56/58 in a circumferential manner. By advancing the anchors 574 duringdeployment, the annular tissue 52 is compressed along the length of thefilament structure 572, thereby closing fractures and fissures 56/58 andreducing posterior protrusions.

A similar arrangement is shown in FIGS. 22C and 22D. In this embodiment,a reinforcement member 580 comprises a monofilament or a multifilamentstructure 582 having a single distal anchor 584 attached thereto. Theproximal end of the filament structure 582 is otherwise free. Duringimplantation, one or more reinforcement members 580 may be utilized asshown in FIG. 22D. The free ends of the filament structure 582 areconnected using, for example, a knot 586 with or without the use of apledget 750.

From the foregoing, those skilled in the art will appreciate that thepresent invention provides reinforcement devices 100, 200, 300, 600,510, 520, 530, 540, 570 and 580, which may be used to reinforce adamaged disc, while permitting relative movement of the adjacentvertebrae. The present invention also provides minimally invasivemethods of implanting such devices as described above.

Those skilled in the art will recognize that the present invention maybe manifested in a variety of forms other than the specific embodimentsdescribed and contemplated herein. Accordingly, departures in form anddetail may be made without departing from the scope and spirit of thepresent invention as described in the appended claims.

What is claimed is:
 1. A method of treating an annulus of anintervertebral disc in a patient's spine, the method comprising thesteps of: providing an elongate member having a treatment length;positioning the treatment length in the annulus of the intervertebraldisc; and while the treatment length is in the annulus, applying therapydirectly to the annulus with the treatment length.
 2. A method as inclaim 1, wherein the step of applying therapy comprises applyingcompression to the annulus with the treatment length.
 3. A method as inclaim 1, wherein the entire treatment length is positioned in theannulus.
 4. A method as in claim 1, wherein the heating length has acircumference, and wherein the heating length is positioned in theannulus such that annular tissue completely surrounds the circumferenceof at least a portion of the heating length.
 5. A method as in claim 1,wherein the treatment length applies heat and compression to theannulus.
 6. A method as in claim 1, wherein the treatment length isimplanted chronically.
 7. A method as in claim 1 wherein the treatmentlength is implanted temporarily.
 8. A method as in claim 1, wherein thestep of applying therapy comprises heating the treatment length todirectly apply heat to the annulus.
 9. A method as in claim 8, whereinthe heat is applied temporarily.
 10. A method of treating an annulus ofan intervertebral disc in a patient's spine, the method comprising thesteps of: providing an elongate member having a heating length;positioning the heating length in the annulus of the intervertebraldisc; and while the heating length is in the annulus, applying heatdirectly to the annulus with the heating length.
 11. A method as inclaim 10, wherein the entire heating length is positioned in theannulus.
 12. A method as in claim 10, wherein the heating length has acircumference, and wherein the heating length is positioned in theannulus such that annular tissue completely surrounds the circumferenceof at least a portion of the heating length.
 13. A method as in claim10, wherein the heat is applied temporarily.
 14. A method as in claim10, wherein the heating length is implanted chronically.
 15. A method asin claim 10 wherein the heating length is implanted temporarily.